Johnston wrote: “I am heartbroken to let you know that I will not be joining the band on the upcoming tours.
“For some time, I have been living with mental health problems which have led to addiction issues that I have kept concealed for a long time.
“This has caused significant problems for myself and everyone around me – the time has come to properly address my illnesses and deal with them.”
He said he was extremely sorry to frontman Simon Neil and his twin brother Ben – the band’s drummer – and thanked them “for their continued love, patience, support and understanding throughout this time”.
Session bassist Naomi MacLeod will step in for the band in the meantime.
The post prompted an outpouring of support from fans.
One said: “Thank you for putting yourself first James. The hardest part is accepting that you need help. We’re here when you’re ready to come back.”
Another added: “Sending loads of love brother. You’ve done the hardest thing which is facing it. We’re all rooting for you.”
